QUATERNARY GEOLOGIC MAPPING OF THE BARRINGTON QUADRANGLE, NE ILLINOIS

Ice flowing southward through the Lake Michigan trough has advanced and retreated over northeastern Illinois several times during the Wisconsin Episode, creating a complex landscape of subglacial topography, end moraines, and outwash plains. Mapping at the 7.5-minute quadrangle scale is providing the detail necessary for a better understanding of the complex glacial processes involved. With the support of the USGS EDMAP program, we have mapped the Quaternary geology of the Barrington Quadrangle. The surficial mapping and stratigraphic studies were completed using engineering and well logs, topographic and soil maps, aerial photos, ISGS sample sets, and a series of core samples (Power Probe) from which magnetic susceptibility, particle size analysis, XRD, and XRF data were acquired. These data assisted in differentiating the diamicton units (Wedron Group), of which four have been identified. Of these, only two are found at the surface in the Barrington Quadrangle. The Wadsworth Formation is a silty clay diamicton and is associated with the N-S trending Valparaiso Moraine. The Haeger Member (Lemont Formation) is a gravelly sandy loam diamicton that is stratigraphically lower than the Wadsworth Formation and is associated with both the NW-SE trending Woodstock Moraine and the N-S trending Fox Lake Moraine to the north of the study area. In the study area, however, the Haeger Member increases in silt percentage from north to south so as to become indistinguishable from the Wadsworth Formation at its southern extent. In the subsurface we have identified the Yorkville Member (Lemont Formation), a silty clay loam diamicton, and the Tiskilwa Formation, a reddish gray clay loam diamicton that is the lowest Wisconsin age diamicton in the area. The extensive outwash along the Fox River has been differentiated into five main terraces. The upper two (T1 and T2) are associated with the formation of the Woodstock and Fox Lake Moraines (Haeger Member), respectively. T3 and T4 are correlated to the formation of the Valparaiso Moraine (Wadsworth Formation), while the lowest (T5) is of late glacial or early Holocene reworking of glacial deposits.